Gas-solid fluidized bed dry beneficiation process using beneficiation density gradient

ABSTRACT

Provided is a gas-solid fluidized bed dry beneficiation process using a beneficiation density gradient, including: in a dry beneficiation system of a gas-solid fluidized bed, selecting coarse particles and fine particles; placing the coarse particles at a bottom of the dry beneficiation system, and placing the fine particles above the coarse particles, wherein the coarse particles and the fine particles are separated under an initial condition; under an effect of a gas flow, the coarse particles and the fine particles being fluidized to form a high-density beneficiation region and a low-density beneficiation region, respectively, and the coarse particles and the fine particles being mixed at a contact interface to form an intermediate-density beneficiation region; and feeding minerals to be beneficiated from an upper portion of the dry beneficiation system to pass through the low-density beneficiation region, the intermediate-density beneficiation region, and the high-density beneficiation region in sequence.

BACKGROUND Technical Field

The present invention relates to a mineral processing method, andbelongs to the technical field of dry mineral beneficiation, and inparticular, relates to a gas-solid fluidized bed dry beneficiationprocess using a beneficiation density gradient.

Description of Related Art

Coal is one of the important basic energy sources in the world, and hasa significant role in promoting the development of the world economy.The huge consumption and yield of coal have brought severe challenges tothe living environment and ecological security of people. Environmentalproblems such as “smog” and “acid rain” have aroused widespread concernfrom governments and people.

Coal beneficiation is a basis for clean utilization of coal, and playsan important role in improving the quality of coal products and inpre-treatment upgrading of coal before combustion. With the increasingshortage of water resources, the gas-solid fluidized bed drybeneficiation technology has attracted the attention of scholars fromChina, Canada, Japan, India, Australia, and other countries. Thegas-solid fluidized bed dry beneficiation technology mainly usesmagnetite minerals as a dense medium, a fluid with a certain density isformed under the effect of a gas flow, and minerals to be beneficiatedare separated according to the density to form light products and heavyproducts, thus having advantages such as a simple process and highbeneficiation precision, and providing an important way for processingand utilization of coal beneficiation. At present, a traditionalgas-solid fluidized bed beneficiation machine mixes two kinds ofparticles with similar aerodynamic diameters to adjust a beneficiationdensity, and a single beneficiation density is formed in a beneficiationsystem. Due to the complex density composition of the minerals to bebeneficiated, the minerals close to the beneficiation density are proneto mismatching, which reduces the beneficiation efficiency and reducesthe quality of products. Chinese invention patent application No.CN1161884 disclosed a method and an apparatus for beneficiating threeproducts using a double-density layer air dense medium fluidized bed,which is mainly used to achieve the purpose of producing three differentminerals. However, it is not difficult to find that adjustment of a lowdensity and a high density mainly depends on selecting the density andsize of particles, without considering the use of particulate expansioncharacteristics of the particles to optimize the adjustment of thebeneficiation density. The fluidized bed used in the beneficiation is aconical inclined surface design with an inclination angle of 60°-80°,which will increase the possibility of forming a spouted bed, and is notconducive to the beneficiation of minerals. The beneficiation density ismainly divided into a high-density beneficiation region formed by heavyand large particles and a low-density beneficiation region formed bylight and small particles. The density gradient has a certainlimitation.

SUMMARY

An objective of the present invention is to overcome the shortcomings ofthe prior art and provide a dry beneficiation system of a gas-solidfluidized bed using a beneficiation density gradient. Coarse particlesand fine particles are selected as beneficiation media, and by means ofa density gradient formed by fluidizing the coarse and fine particles,the mineral beneficiation efficiency is improved.

In order to achieve the above objective, a gas-solid fluidized bed drybeneficiation process using a beneficiation density gradient is providedin the present invention, including: in a dry beneficiation system of agas-solid fluidized bed, selecting coarse particles and fine particlesas beneficiation media, wherein an aerodynamic diameter of the coarseparticles is greater than an aerodynamic diameter of the fine particles,and an aerodynamic diameter ratio of the coarse particles to the fineparticles is not greater than 10; placing the coarse particles at abottom of the dry beneficiation system of the gas-solid fluidized bed,and placing the fine particles above the coarse particles, wherein thecoarse particles and the fine particles are in a completely separatedstate under an initial condition; under an effect of a gas flow, thecoarse particles and the fine particles beginning to be fluidized toform a high-density beneficiation region and a low-density beneficiationregion, respectively, and the coarse particles and the fine particlesbeing in a mixed state at a contact interface to form anintermediate-density beneficiation region; and feeding minerals to bebeneficiated from an upper portion of the dry beneficiation system ofthe gas-solid fluidized bed to pass through the low-densitybeneficiation region, the intermediate-density beneficiation region, andthe high-density beneficiation region in sequence, to complete abeneficiation of the minerals.

Preferably, a size of the coarse particles and a size of the fineparticles are not greater than 500 μm, and the size of the coarseparticles is greater than the size of the fine particles, and the sizeof the coarse particles is uniform or non-uniform, and the size of thefine particles is uniform or non-uniform, and a density of the coarseparticles is not less than a density of the fine particles. The size andthe density of the coarse particles and the size and the density of thefine particles are determined according to requirements of abeneficiation density.

Preferably, an initial height of the coarse particles and an initialheight of the fine particles are 20-100 cm; and more preferably, theinitial height of the coarse particles and the initial height of thefine particles are 20-50 cm.

Preferably, a minimum fluidization velocity of the coarse particles isgreater than a minimum fluidization velocity of the fine particles, anda terminal velocity of the coarse particles is greater than a terminalvelocity of the fine particles.

Preferably, an operating gas velocity is higher than a minimumfluidization gas velocity of the coarse particles and lower than theterminal velocity of the fine particles, and the operating gas velocityis 60% of a difference between the terminal velocity of the fineparticles and the minimum fluidization velocity of the coarse particles.

Preferably, a particle size of the minerals to be beneficiated is notgreater than 300 mm, and more preferably, the particle size of theminerals to be beneficiated is 0.5-100 mm.

Preferably, in the dry beneficiation system of the gas-solid fluidizedbed, a density adjustment range of a beneficiation bed is 1.0-2.6 g/cm³,and more preferably, the density adjustment range of the beneficiationbed is 1.3-2.0 g/cm³.

A fluid for fluidizing medium particles may include a series of gasessuch as air, carbon dioxide, and nitrogen, and preferably include air.

Compared with the traditional gas-solid fluidized bed dry beneficiationtechnology, the present invention strengthens the beneficiation ofminerals through the density gradient (high density, intermediatedensity, and low density) formed by the fluidization of the coarse andfine particles, which can improve the accuracy of beneficiation, andrealize high-efficient dry beneficiation of coal. In addition, theapparatus of the present invention does not use water, and is simple inoperation and maintenance, pollution free, and low in investment andoperating costs, thus having significant economic and social benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a dry beneficiation system of agas-solid fluidized bed using a beneficiation density gradient toenhance mineral beneficiation according to the present invention.

In FIG. 1, 1—fine particles; 2—coarse particles; 3—low-densitybeneficiation region; 4—intermediate-density beneficiation region; and5—high-density beneficiation region.

DESCRIPTION OF THE EMBODIMENTS

In order to better understand the present invention, description is madebelow with reference to the accompanying drawings and examples.

As shown in FIG. 1, in a dry beneficiation system of a gas-solidfluidized bed, coarse particles 2 and fine particles 1 are selected asbeneficiation media, an aerodynamic diameter of the coarse particles 2is greater than an aerodynamic diameter of the fine particles 1, and anaerodynamic diameter ratio of the coarse particles 2 to the fineparticles 1 is not greater than 10 (the aerodynamic diameter is directlyrelated to a sedimentation behavior of particles, and reflectshydrodynamic characteristics of the coarse particles and the fineparticles. The aerodynamic diameter is defined as a diameter of a spherewith a unit density (1 g/cm³), while moving in still air at a lowReynolds number, reaching the same final settling velocity as the actualparticle). The coarse particles 2 are placed at a bottom of the drybeneficiation system of the gas-solid fluidized bed, the fine particles1 are placed above the coarse particles 2, and the coarse particles 2and the fine particles 1 are in a completely separated state under aninitial condition. Under the effect of a gas flow, the coarse particles2 and the fine particles 1 begin to be fluidized to form a high-densitybeneficiation region 5 and a low-density beneficiation region 3,respectively. The coarse particles 2 and the fine particles 1 are in amixed state at a contact interface to form an intermediate-densitybeneficiation region 4. A beneficiation density of the low-densitybeneficiation region 3 is less than a density required for beneficiationof the minerals to be beneficiated, a beneficiation density of theintermediate-density beneficiation region 4 is close to the densityrequired for the beneficiation of the minerals to be beneficiated, and abeneficiation density of the high-density beneficiation region 5 isgreater than or equal to the density required for the beneficiation ofthe minerals to be beneficiated. The minerals to be beneficiated are fedfrom an upper portion of the dry beneficiation system of the gas-solidfluidized bed, and pass through the low-density beneficiation region 3,the intermediate-density beneficiation region 4, and the high-densitybeneficiation region 5 in sequence. Minerals with a low density thatfloat on the upper portion of the dry beneficiation system of thegas-solid fluidized bed are referred to as light products, and mineralswith a high density that sink into middle and lower portions of the drybeneficiation system of the gas-solid fluidized bed are referred to asheavy products, thus completing the beneficiation of minerals.

Sizes of both the coarse particles and the fine particles are notgreater than 500 μm, the size of the coarse particles is greater thanthe size of the fine particles, the size of the coarse particles 2 isuniform or non-uniform, the size of the fine particles 1 is uniform ornon-uniform, a density of the coarse particles 2 is not less than thatof the fine particles 1, and the sizes and densities of the coarseparticles and the fine particles are determined according torequirements of a beneficiation density.

Initial heights of the coarse particles 2 and the fine particles 1 areboth 20-100 cm; and more preferably, the initial heights of the coarseparticles 2 and the fine particles 1 are both 20-50 cm.

A minimum fluidization velocity of the coarse particles 2 is greaterthan a minimum fluidization velocity of the fine particles 1, and aterminal velocity of the coarse particles 2 is greater than a terminalvelocity of the fine particles 1.

A fluid for fluidizing medium particles may include a series of gasessuch as air, carbon dioxide, and nitrogen, and preferably include air.In an actual beneficiation process, an operating gas velocity is higherthan a minimum fluidization gas velocity of the coarse particles andlower than the terminal velocity of the fine particles, and theoperating gas velocity is selected to be about 60% of a differencebetween the terminal velocity of the fine particles and the minimumfluidization velocity of the coarse particles.

A particle size of the minerals that can be beneficiated in the presentinvention is not greater than 300 mm, and is preferably 0.5-100 mm. Adensity adjustment range of the dry beneficiation system of thegas-solid fluidized bed is 1.0-2.6 g/cm³, and an optimal beneficiationdensity is 1.3-2.0 g/cm³.

A detailed description of an application process of the gas-solidfluidized bed dry beneficiation process using a beneficiation densitygradient is made below in combination with an instance of coalbeneficiation.

Embodiment 1

High-density beneficiation is required for coal samples, and abeneficiation density is required to be greater than 1900 kg/m³. Coarsemagnetite powder (with an average particle size d_(p)=100 μm, and a truedensity ρ=4600 kg/m³) and fine magnetite powder (with an averageparticle size d_(p)=45 μm, and a true density ρ=4600 kg/m³) are selectedas medium particles. A static stacking height of the two kinds of mediumparticles is 30 cm, respectively. Air is selected as a gas required forfluidizing the medium particles, and is fed from a bottom of thebeneficiation system. The density of coarse particles formed under theeffect of an air flow is about 2100 kg/m³, which is referred to as ahigh-density beneficiation region. The density of fine particles formedunder the effect of the air flow is about 1800 kg/m³, which is referredto as a low-density beneficiation region. The density formed at acontact interface of the two kinds of particles is about 1900 kg/m³,which is referred to as an intermediate-density beneficiation region.The coal samples are preliminarily sieved, and coal samples with adiameter of 6-50 mm are used as minerals to be beneficiated. Afterpassing through the low-density beneficiation region, minerals with adensity far less than the low-density region of the bed float on anupper portion of the dry beneficiation system of the gas-solid fluidizedbed. After passing through the intermediate-density beneficiationregion, the preliminary beneficiated samples are further beneficiated,which helps to complete further separation of coal and gangue. Afterpassing through the high-density beneficiation region, minerals with alarge density that sink into middle and lower portions of the drybeneficiation system of the gas-solid fluidized bed are referred to asheavy products, and complete beneficiation of minerals is finallyrealized.

Embodiment 2

Low-density beneficiation is required for coal samples, and abeneficiation density is required to be greater than 1300 kg/m³. Quartzsand (with an average particle size d_(p)=100 μm, and a true densityρ=2600 kg/m³) and quartz sand (with an average particle size d_(p)=40μm, and a true density ρ=2600 kg/m³) are selected as medium particles. Astatic stacking height of the two kinds of medium particles is 20 cm,respectively. Air is selected as a gas required for fluidizing themedium particles, and is fed from a bottom of the beneficiation system.The density of coarse particles formed under the effect of an air flowis about 1500 kg/m³, which is referred to as a high-densitybeneficiation region. The density of fine particles formed under theeffect of the air flow is about 1300 kg/m³, which is referred to as alow-density beneficiation region. The density formed at a contactinterface of the two kinds of particles is about 1100 kg/m³, which isreferred to as an intermediate-density beneficiation region. The coalsamples are preliminarily sieved, and coal samples with a diameter of6-50 mm are used as minerals to be beneficiated. After passing throughthe low-density beneficiation region, minerals with a density far lessthan the low-density region of the bed float on an upper portion of thedry beneficiation system of the gas-solid fluidized bed. After passingthrough the intermediate-density beneficiation region, the preliminarybeneficiated samples are further beneficiated, which helps to completefurther separation of coal and gangue. After passing through thehigh-density beneficiation region, minerals with a large density thatsink into middle and lower portions of the dry beneficiation system ofthe gas-solid fluidized bed are referred to as heavy products, andcomplete beneficiation of minerals is finally realized.

The above are only the preferred embodiments of the present invention,and are not intended to limit the present invention. It should bepointed out that for those of ordinary skill in the art, severalimprovements and modifications can be made without departing from theprinciple of the present invention, and these improvements andmodifications should also be regarded as the protection scope of thepresent invention.

1. A gas-solid fluidized bed dry beneficiation process using abeneficiation density gradient, comprising: in a dry beneficiationsystem of a gas-solid fluidized bed, selecting coarse particles and fineparticles as beneficiation medium particles, wherein an aerodynamicdiameter of the coarse particles is greater than an aerodynamic diameterof the fine particles, and an aerodynamic diameter ratio of the coarseparticles to the fine particles is not greater than 10; placing thecoarse particles at a bottom of the dry beneficiation system of thegas-solid fluidized bed, and placing the fine particles above the coarseparticles, wherein the coarse particles and the fine particles are in acompletely separated state under an initial condition; under an effectof a gas flow, the coarse particles and the fine particles beginning tobe fluidized to form a high-density beneficiation region and alow-density beneficiation region, respectively, and the coarse particlesand the fine particles being in a mixed state at a contact interface toform an intermediate-density beneficiation region; and feeding mineralsto be beneficiated from an upper portion of the dry beneficiation systemof the gas-solid fluidized bed to pass through the low-densitybeneficiation region, the intermediate-density beneficiation region, andthe high-density beneficiation region in sequence, to complete abeneficiation of the minerals.
 2. The gas-solid fluidized bed drybeneficiation process using the beneficiation density gradient accordingto claim 1, wherein a size of the coarse particles and a size of thefine particles are not greater than 500 μm, and the size of the coarseparticles is greater than the size of the fine particles, and the sizeof the coarse particles is uniform or non-uniform, and the size of thefine particles is uniform or non-uniform, and a density of the coarseparticles is not less than a density of the fine particles.
 3. Thegas-solid fluidized bed dry beneficiation process using thebeneficiation density gradient according to claim 1, wherein an initialheight of the coarse particles and an initial height of the fineparticles are 20-100 cm.
 4. The gas-solid fluidized bed drybeneficiation process using the beneficiation density gradient accordingto claim 3, wherein the initial height of the coarse particles and theinitial height of the fine particles are 20-50 cm.
 5. The gas-solidfluidized bed dry beneficiation process using the beneficiation densitygradient according to claim 1, wherein a minimum fluidization velocityof the coarse particles is greater than a minimum fluidization velocityof the fine particles, and a terminal velocity of the coarse particlesis greater than a terminal velocity of the fine particles.
 6. Thegas-solid fluidized bed dry beneficiation system using the beneficiationdensity gradient according to claim 1, wherein an operating gas velocityis higher than a minimum fluidization gas velocity of the coarseparticles and lower than a terminal velocity of the fine particles, andthe operating gas velocity is 60% of a difference between the terminalvelocity of the fine particles and a minimum fluidization velocity ofthe coarse particles.
 7. The gas-solid fluidized bed dry beneficiationsystem using the beneficiation density gradient according to claim 1,wherein a particle size of the minerals to be beneficiated is notgreater than 300 mm.
 8. The gas-solid fluidized bed dry beneficiationprocess using the beneficiation density gradient according to claim 7,wherein the particle size of the minerals to be beneficiated is 0.5-100mm.
 9. The gas-solid fluidized bed dry beneficiation process using thebeneficiation density gradient according to claim 1, wherein in the drybeneficiation system of the gas-solid fluidized bed, a densityadjustment range of a beneficiation bed is 1.0-2.6 g/cm³.
 10. Thegas-solid fluidized bed dry beneficiation process using thebeneficiation density gradient according to claim 9, wherein in the drybeneficiation system of the gas-solid fluidized bed, the densityadjustment range of the beneficiation bed is 1.3-2.0 g/cm³.